The invention relates to a non-CT type radiation tomography device for carrying out a radiation tomography for a subject or object to be examined (hereinafter referred to simply as xe2x80x9csubjectxe2x80x9d).
A system for examining the subject without destruction by using X-rays has a relatively long history, and there are a simple X-ray photographing system wherein X-rays are irradiated to the subject and at the same time a transmitted X-ray image is detected by an X-ray film, imaging plate or image intensifier, i.e. I. I. Tube, to thereby take an image; and an X-ray tomography system wherein an image of a specific section of the subject is taken. In regard to the latter X-ray tomography system, there is a non-CT type tomography system which has been developed from the simple X-ray photographing system prior to an X-ray CT type, not the tomography system of the X-ray CT, i.e. X-ray computerized tomography type which has been developed remarkably. FIG. 17 is a diagram showing a structure of a photographing system in a conventional non-CT type X-ray tomography (hereinafter, referred to as xe2x80x9cX-ray tomographyxe2x80x9d).
In the conventional non-CT type X-ray tomography system, a subject M is rotated around a rotation axis ra, which has an intersection Ma with an X-ray irradiation axis, i.e. radiation irradiating axis Xa, of an X-ray tube R in the subject M. A detecting surface Da of a sheet-type X-ray detector D for detecting a transmitted or passed X-ray image of the subject M is held perpendicular to the rotation axis ra of the subject. An X-ray fault picture image (hereinafter referred to as xe2x80x9cfault picture imagexe2x80x9d) can be obtained by integration of the transmitted X-ray picture images sequentially obtained based on detected data outputted from the sheet-type X-ray detector D as X-rays are irradiated to the subject M and the subject M is rotated. The reason why the fault picture image can be obtained by integrating the transmitted X-ray picture images is specifically explained hereunder.
As shown in FIG. 17, the subject M has a section MA parallel to the detecting surface Da of the sheet-type X-ray detector D including an intersection Ma, and a section MB parallel to the detecting surface Da of the sheet-type X-ray detector D without including the intersection Ma in the subject M. Here, as shown in FIG. 18(a), the section MA has an X-ray shielding area with an A-character shape, and as shown in FIG. 18(b), the section MB has an X-ray shielding area with a B-character shape. Therefore, in the respective transmitted X-ray picture images sequentially obtained based on the detected data outputted from the sheet-type X-ray detector D, for example, as shown in FIG. 18(c), an A-character shape image and a B-character shape image coexist. However, a position of the A-character shape image is always fixed at the center of the picture image, and a position of the B-character shape is moved in a clockwise direction around the A-character shape image as the subject M is rotated. As a result, as shown in FIG. 18(d), in an integrated picture image of all the transmitted X-ray picture images, although the A-character shape image becomes clear due to overlapping of all the images, the B-character shape images become unclear, obscure, by being scattered in all directions. Thus, the picture image of FIG. 18(d) becomes an X-ray fault picture image emphasizing the section MA.
As described above, the non-CT type X-ray tomography system has almost the same structure as that of the simple X-ray photographing system to photograph a specific section in the subject M, so that a fault picture image can be obtained.
However, in the above conventional X-ray tomography system, it has been difficult to set an accurate photographing mode according to a photographing state. According to an object for photographing, a subject or a state of the subject M, even if an emphasizing degree of the section MA is weak, i.e. a resolving power or resolution ability in a depth direction of the fault picture image is low, there may be a case where a photographing mode having a wide photographing area is desired; or even if a photographing area is narrow, there may be a case where a photographing mode having a strong emphasizing degree, i.e. a high resolving power in a depth direction of the fault picture image, of the section MA is desired. However, in the conventional X-ray tomography system, since the range of the photographing mode which can be set is very narrow, it is difficult to set a suitable photographing mode according to a photographing condition.
In view of the above defects, the present invention has been made, and an object of the invention is to provide a radiation tomography device having various photographing modes capable of freely setting a suitable photographing mode according to a photographing situation, and a subject examination apparatus using the same.
Further objects and advantages of the invention will be apparent from the following description of the invention.
In order to attain the above objects, according to a first aspect of the invention, a radiation tomography device comprises an irradiation device for irradiating radiations to a subject; a radiation detector for detecting a transmitted or passed radiation image of the subject; a subject holding and rotating device for rotating the subject around a rotation axis intersecting a radiation irradiating axis in the subject; a Laminographic angle variation device for varying an angle, i.e. Laminographic angle, formed by the radiation irradiating axis and the rotation axis; a picture image processing device for obtaining a radiation fault picture image by storing and calculating the transmitted or passed radiation picture images sequentially obtained based on detected data outputted from the radiation detector as the radiations are irradiated to the subject by the irradiation device and the subject is rotated by the subject holding and rotating device; and a picture image display device for displaying a fault picture image obtained by the picture image processing device.
According to a second aspect of the invention, in the radiation tomography device of the first aspect, the Laminographic angle variation device is structured such that the Laminographic angle is varied by changing an inclination angle of the radiation irradiating axis with respect to the rotation axis of the subject.
According to a third aspect of the invention, in the radiation tomography device of the first aspect, the Laminographic angle variable device is structured such that the Laminographic angle is varied by changing an inclination angle of the rotation axis of the subject with respect to the radiation irradiating axis.
According to a fourth aspect of the invention, the radiation tomography device of the first aspect includes a posture holding device for holding the detecting surface of the radiation detector perpendicular to the rotation axis of the subject.
According to a fifth aspect of the invention, the radiation tomography device of the fourth aspect includes a synchronous rotation device for rotating the detecting surface in synchronism with rotation of the subject around an axis perpendicular to the detecting surface and passing through an intersection of the radiation irradiating axis and the detecting surface, in a state where the detecting surface of the radiation detector is held perpendicular to the rotation axis of the subject.
According to a sixth aspect of the invention, the radiation tomography device of any one of the first to fifth aspects includes a position changing device for changing a position of the subject with respect to the intersection of the radiation irradiating axis and the rotation axis.
According to a seventh aspect of the invention, the radiation tomography device of any one of the first to sixth aspects includes a distance varying device for varying a distance between the subject and the radiation irradiating device in a direction of the radiation irradiating axis and/or a distance between the subject and the radiation detector.
In an eighth aspect of the invention, a subject examination apparatus comprises a subject transferring device sequentially transferring subjects along a predetermined transferring route; an irradiating device for irradiating radiations to the subject transferred by the subject transferring device; a radiation detector for detecting a transmitted or passed radiation picture image of the subject; a subject rotating device for rotating the subject around a rotation axis intersecting the radiation irradiating axis in the subject; a posture holding device for holding the detecting surface of the radiation detector perpendicular to the rotation axis of the subject; a Laminographic angle variation device for varying an angle, i.e. Laminographic angle, formed by the radiation irradiating axis and the rotation axis; a picture image processing device for obtaining a fault picture image by storing and calculating transmitted or passed radiation picture images sequentially obtained based on detected data outputted from the radiation detector as radiations are irradiated by the irradiating device and the subject is rotated by the subject rotating device; and a picture image display device for displaying the radiation fault picture image obtained by the picture image processing device.
According to a ninth aspect of the invention, the subject examination apparatus of the eighth aspect is structured such that the irradiating device and the radiation detector are separately disposed above and under the transferring route of the subject.
According to a tenth aspect of the invention, the subject examination apparatus of the eighth or ninth aspect is structured such that the subject rotating device, the irradiating device and the radiation detector are disposed on a way of the subject transferring device. When the subject is transferred to a position of the subject rotating device, transfer of the subject is once stopped to rotate the subject, and at the same time, the irradiation is carried out by the irradiating device and the transmitted radiation picture images are detected by the radiation detector.
Next, operation when the radiation fault picture image is obtained by the device according to the invention, is explained.
In the tomography by the device according to the invention, the subject is rotated around the rotation axis intersecting the radiation irradiating axis of the irradiating device in the subject. Further, by storing and calculating the transmitted or passed radiation picture images in the picture image processing device, sequentially obtained based on the detected data outputted from the radiation detector as the subject is rotated and X-rays are irradiated to the subject, there is formed a fault picture image emphasizing a section, i.e. section of a portion to be photographed, parallel to the detecting surface of the radiation detector including the intersection of the radiation irradiating axis and the rotation axis, and the fault picture image is displayed on the image display device.
According to the device of the present invention, since a balance between the emphasizing degree of the section of the subject and the photographing area can be adjusted by varying the Laminographic angle through the Laminographic angle variable device, the photographing modes corresponding to the photographing situations can be freely set.
In the device according to the second aspect of the invention, the Laminographic angle is changed by the Laminographic angle variation device to correspond to a changed portion of an inclination angle of the radiation irradiating axis with respect to the rotation axis of the subject.
In the device according to the third aspect of the invention, the Laminographic angle is changed by the Laminographic angle variation device to correspond to a changed portion of an inclination angle of the rotation axis of the subject with respect to the radiation irradiating axis.
In the device according to the fourth aspect of the invention, since the detecting surface of the radiation detector is held perpendicular to the rotating axis of the subject by the posture holding device, in case a fault picture image of a section parallel to the detecting surface of the radiation detector is obtained, a load of operational process is reduced.
In the device according to the fifth aspect of the invention, the detecting surface is rotated in synchronism with rotation of the subject around an axis perpendicular to the detecting surface and passing through an intersection where the radiation irradiating axis crosses the detecting surface in a state where the detecting surface of the radiation detector is held perpendicularly by the synchronous rotation device. As a result, since a direction of the detecting surface of the radiation detector and a direction of the subject are unchangeable, when the storage and calculation of transmitted radiation picture images are carried out, a process for arranging the directions of the images is not required. In case the direction of the detecting surface of the radiation detector and the direction of the subject are changed, when the storage and calculation of the transmitted radiation picture images are carried out, the process for arranging the directions of the picture images is required.
In the device of the sixth aspect of the invention, as a position of the subject is changed with respect to the intersection of the radiation irradiating axis and the rotating axis, since a section including the intersection is changed, the section of the subject is also changed.
In the device of the seventh aspect of the invention, as a distance between the subject and the irradiating device in a direction of the radiation irradiating axis and/or a distance between the subject and the radiation detector is changed by a distance varying device, the size of the transmitted radiation picture image projected on the detecting surface is changed to thereby change the magnitude of the transmitted radiation picture image, so that a magnification of the final fault picture image is changed.
In the subject examining apparatus of the eighth aspect of the invention, a suitable Laminographic angle is set with respect to each of the subjects sequentially transferred along the predetermined transferring route by the subject transferring device, and an accurate radiation fault picture image can be obtained by taking a tomography of each of the subjects with a photographing mode suitable for a situation by adjusting a balance between the resolution capability in a depth direction of the fault picture image of the subject and the photographing area thereof.
In the apparatus of the ninth aspect of the invention, since the radiation irradiating device and the radiation detector are separately disposed above and under the transferring route of the subject, dimension in a widthwise direction of the apparatus can be reduced when compared with a case where the radiation irradiating device and the radiation detector are separately disposed on both left and right sides to cross the transferring route of the subjects.
In the apparatus of the tenth aspect of the invention, when the subject is transferred to a position where the subject rotating device is disposed, the transfer of the subject is once stopped; the subject is rotated by the subject rotating device and irradiated with the radiations by the irradiating device; and the transmitted radiation picture images are quickly detected by the radiation detector to thereby automatically carry out the tomography of the subject.